scholarly journals Specificity of repeat-induced point mutation (RIP) in Neurospora: sensitivity of non-Neurospora sequences, a natural diverged tandem duplication, and unique DNA adjacent to a duplicated region.

Genetics ◽  
1991 ◽  
Vol 127 (4) ◽  
pp. 711-717 ◽  
Author(s):  
E J Foss ◽  
P W Garrett ◽  
J A Kinsey ◽  
E U Selker
Keyword(s):  
Sequence Analysis ◽  
Point Mutation ◽  
Dna Sequence ◽  
Dna Sequences ◽  
Tandem Duplication ◽  
Sexual Cycle ◽  
Hygromycin B ◽  
Plasmid Puc8 ◽  
The Stability ◽  
Repeat Induced Point Mutation

Abstract The process designated RIP (repeat-induced point mutation) alters duplicated DNA sequences in the sexual cycle of Neurospora crassa. We tested whether non-Neurospora sequences are susceptible to RIP, explored the basis for the observed immunity to this process of a diverged tandem duplication that probably arose by a natural duplication followed by RIP (the Neurospora zeta-eta region), and investigated whether RIP extends at all into unique sequences bordering a duplicated region. Bacterial sequences of the plasmid pUC8 and of a gene conferring resistance to hygromycin B were sensitive to RIP in N. crassa when repeated in the genome. When the entire 1.6-kb zeta-eta region was duplicated, it was susceptible to RIP, but was affected by it to a lesser extent than other duplications. Only three of 62 progeny from crosses harboring unlinked duplications of the region showed evidence of changes. We attribute the low level of alterations to depletion of mutable sites. The stability of the zeta-eta region in strains having single copies of the region suggests that the 14% divergence of the tandem elements is sufficient to prevent RIP. DNA sequence analysis of unduplicated pUC8 sequences adjacent to a duplication revealed that RIP continued at least 180 bp beyond the boundary of the duplication. Three mutations occurred in the 200-bp segment of bordering sequences examined.

scholarly journals High frequency repeat-induced point mutation (RIP) is not associated with efficient recombination in Neurospora.

Genetics ◽  
1994 ◽  
Vol 138 (4) ◽  
pp. 1093-1103 ◽  
Author(s):  
J T Irelan ◽  
A T Hagemann ◽  
E U Selker
Keyword(s):  
Point Mutation ◽  
Dna Sequences ◽  
High Frequency ◽  
Recombination Frequency ◽  
Single Copy ◽  
Sexual Cycle ◽  
Base Pairs ◽  
Copy Gene ◽  
The Relationship ◽  
Repeat Induced Point Mutation

Abstract Duplicated DNA sequences in Neurospora crassa are efficiently detected and mutated during the sexual cycle by a process named repeat-induced point mutation (RIP). Linked, direct duplications have previously been shown to undergo both RIP and deletion at high frequency during premeiosis, suggesting a relationship between RIP and homologous recombination. We have investigated the relationship between RIP and recombination for an unlinked duplication and for both inverted and direct, linked duplications. RIP occurred at high frequency (42-100%) with all three types of duplications used in this study, yet recombination was infrequent. For both inverted and direct, linked duplications, recombination was observed, but at frequencies one to two orders of magnitude lower than RIP. For the unlinked duplication, no recombinants were seen in 900 progeny, indicating, at most, a recombination frequency nearly three orders of magnitude lower than the frequency of RIP. In a direct duplication, RIP and recombination were correlated, suggesting that these two processes are mechanistically associated or that one process provokes the other. Mutations due to RIP have previously been shown to occur outside the boundary of a linked, direct duplication, indicating that RIP might be able to inactivate genes located in single-copy sequences adjacent to a duplicated sequence. In this study, a single-copy gene located between elements of linked duplications was inactivated at moderate frequencies (12-14%). Sequence analysis demonstrated that RIP mutations had spread into these single-copy sequences at least 930 base pairs from the boundary of the duplication, and Southern analysis indicated that mutations had occurred at least 4 kilobases from the duplication boundary.

Cytosine Methylation Associated With Repeat-Induced Point Mutation Causes Epigenetic Gene Silencing in Neurospora crassa

Genetics ◽  
1997 ◽  
Vol 146 (2) ◽  
pp. 509-523 ◽  
Author(s):  
Jeffrey T Irelan ◽  
Eric U Selker
Keyword(s):  
Neurospora Crassa ◽  
Point Mutation ◽  
Dna Sequences ◽  
Cytosine Methylation ◽  
Single Copy ◽  
Sexual Cycle ◽  
Epigenetic Gene Silencing ◽  
Flanking Sequences ◽  
Methylation Patterns ◽  
Repeat Induced Point Mutation

Repeated DNA sequences are frequently mutated during the sexual cycle in Neurospora crassa by a process named repeat-induced point mutation (RIP). RIP is often associated with methylation of cytosine residues in and around the mutated sequences. Here we demonstrate that this methylation can silence a gene located in nearby, unique sequences. A large proportion of strains that had undergone RIP of a linked duplication flanking a single-copy transgene, hph (hygromycin B phosphotransferase), showed partial silencing of hph. These strains were all heavily methylated throughout the single-copy hph sequences and the flanking sequences. Silencing was alleviated by preventing methylation, either by 5-azacytidine (5AC) treatment or by introduction of a mutation (eth-I) known to reduce intracellular levels of S-adenosylmethionine. Silenced strains exhibited spontaneous reactivation of hph at frequencies of 10–4 to 0.5. Reactivated strains, as well as cells that were treated with 5AC, gave rise to cultures that were hypomethylated and partially hygromycin resistant, indicating that some of the original methylation was propagated by a maintenance mechanism. Gene expression levels were found to be variable within a population of clonally related cells, and this variation was correlated with epigenetically propagated differences in methylation patterns.

scholarly journals Recurrence of repeat-induced point mutation (RIP) in Neurospora crassa.

Genetics ◽  
1991 ◽  
Vol 127 (4) ◽  
pp. 699-710 ◽  
Author(s):  
E B Cambareri ◽  
M J Singer ◽  
E U Selker
Keyword(s):  
Neurospora Crassa ◽  
Point Mutation ◽  
Dna Sequences ◽  
High Frequency ◽  
First Generation ◽  
Vegetative Cells ◽  
Homologous Sequences ◽  
Sequences Analysis ◽  
The Stability ◽  
Repeat Induced Point Mutation

Abstract Duplicate DNA sequences in the genome of Neurospora crassa can be detected and mutated in the sexual phase of the life cycle by a process termed RIP (repeat-induced point mutation). RIP occurs in the haploid nuclei of fertilized, premeiotic cells before fusion of the parental nuclei. Both copies of duplications of gene-sized sequences are affected in the first generation at frequencies of approximately 50-100%. We investigated the extent to which sequences altered by RIP remain susceptible to this process in subsequent generations. Duplications continued to be sensitive to RIP, even after six generations. The fraction of progeny showing evidence of RIP decreased rapidly, however, apparently as a function of the extent of divergence of the duplicated sequences. Analysis of the stability of heteroduplexes of DNA altered by RIP and their native counterpart indicated that linked duplications diverged further than did unlinked duplications. DNA methylation, a common feature of sequences altered by RIP, did not seem to inhibit the process. A sequence that had become resistant to RIP was cloned and reintroduced into Neurospora in one or more copies to investigate the basis of the resistance. The altered sequence regained its methylation in vegetative cells, indicating that the methylation of sequences altered by RIP observed in vegetative cells is a consequence of the mutations. Duplication of the sequence restored its sensitivity to RIP suggesting that resistance to the process was due to loss of similarity between the duplicated sequences. Consistent with this, we found that the resistant sequence did not trigger RIP of the native homologous sequences of the host, even when no other partner was available. High frequency intrachromatid recombination, which is temporally associated with RIP, was more sensitive than RIP to alterations in the interacting sequences.

scholarly journals Action of Repeat-Induced Point Mutation on Both Strands of a Duplex and on Tandem Duplications of Various Sizes in Neurospora

Genetics ◽  
1999 ◽  
Vol 153 (2) ◽  
pp. 705-714 ◽  
Author(s):  
Michael K Watters ◽  
Thomas A Randall ◽  
Brian S Margolin ◽  
Eric U Selker ◽  
David R Stadler
Keyword(s):  
Point Mutation ◽  
Dna Sequence ◽  
Differential Effect ◽  
Tandem Repeats ◽  
Sequence Data ◽  
Sexual Cycle ◽  
C To T Mutations ◽  
Sequence Bias ◽  
Tandem Duplications ◽  
Repeat Induced Point Mutation

Abstract In Neurospora crassa, DNA sequence duplications are detected and altered efficiently during the sexual cycle by a process known as RIP (repeat-induced point mutation). Affected sequences are subjected to multiple GC-to-AT mutations. To explore the pattern in which base changes are laid down by RIP we examined two sets of strains. First, we examined the products of a presumptive spontaneous RIP event at the mtr locus. Results of sequencing suggested that a single RIP event produces two distinct patterns of change, descended from the two strands of an affected DNA duplex. Equivalent results were obtained using an exceptional tetrad from a cross with a known duplication flanking the zeta-eta (ζ-η) locus. The mtr sequence data were also used to further examine the basis for the differential severity of C-to-T mutations on the coding and noncoding strands in genes. The known bias of RIP toward CpA/TpG sites in conjunction with the sequence bias of Neurospora accounts for the differential effect. Finally, we used a collection of tandem repeats (from 16 to 935 bp in length) within the mtr gene to examine the length requirement for RIP. No evidence of RIP was found with duplications shorter than 400 bp while all longer tandem duplications were frequently affected. A comparison of these results with vegetative reversion data for the same duplications is consistent with the idea that reversion of long tandem duplications and RIP share a common step.

scholarly journals Occurrence of Repeat Induced Point Mutation in Long Segmental Duplications of Neurospora

Genetics ◽  
1997 ◽  
Vol 147 (1) ◽  
pp. 125-136 ◽  
Author(s):  
David D Perkins ◽  
Brian S Margolin ◽  
Eric U Selker ◽  
S D Haedo
Keyword(s):  
Point Mutation ◽  
Sexual Cycle ◽  
Segmental Duplications ◽  
Wild Type ◽  
Single Chain ◽  
Base Pairs ◽  
Gene Size ◽  
Type Gene ◽  
Repeat Induced Point Mutation

Abstract Previous studies of repeat induced point mutation (RIP) have typically involved gene-size duplications resulting from insertion of transforming DNA at ectopic chromosomal positions. To ascertain whether genes in larger duplications are subject to RIP, progeny were examined from crosses heterozygous for long segmental duplications obtained using insertional or quasiterminal translocations. Of 17 distinct mutations from crossing 11 different duplications, 13 mapped within the segment that was duplicated in the parent, one was closely linked, and three were unlinked. Half of the mutations in duplicated segments were at previously unknown loci. The mutations were recessive and were expressed both in haploid and in duplication progeny from Duplication × Normal, suggesting that both copies of the wild-type gene had undergone RIP. Seven transition mutations characteristic of RIP were found in 395 base pairs (bp) examined in one ro-11 allele from these crosses and three were found in ~750 bp of another. A single chain-terminating C to T mutation was found in 800 bp of arg-6. RIP is thus responsible. These results are consistent with the idea that the impaired fertility that is characteristic of segmental duplications is due to inactivation by RIP of genes needed for progression through the sexual cycle.

scholarly journals Synthesis of Signals for De Novo DNA Methylation in Neurospora crassa

2003 ◽  
Vol 23 (7) ◽  
pp. 2379-2394 ◽  
Author(s):  
Hisashi Tamaru ◽  
Eric U. Selker
Keyword(s):  
Dna Methylation ◽  
Neurospora Crassa ◽  
Point Mutation ◽  
Dna Sequences ◽  
De Novo ◽  
Test Site ◽  
Minor Groove ◽  
Binding Motif ◽  
Repeat Induced Point Mutation

ABSTRACT Most 5-methylcytosine in Neurospora crassa occurs in A:T-rich sequences high in TpA dinucleotides, hallmarks of repeat-induced point mutation. To investigate how such sequences induce methylation, we developed a sensitive in vivo system. Tests of various 25- to 100-bp synthetic DNA sequences revealed that both T and A residues were required on a given strand to induce appreciable methylation. Segments composed of (TAAA) n or (TTAA) n were the most potent signals; 25-mers induced robust methylation at the special test site, and a 75-mer induced methylation elsewhere. G:C base pairs inhibited methylation, and cytosines 5′ of ApT dinucleotides were particularly inhibitory. Weak signals could be strengthened by extending their lengths. A:T tracts as short as two were found to cooperate to induce methylation. Distamycin, which, like the AT-hook DNA binding motif found in proteins such as mammalian HMG-I, binds to the minor groove of A:T-rich sequences, suppressed DNA methylation and gene silencing. We also found a correlation between the strength of methylation signals and their binding to an AT-hook protein (HMG-I) and to activities in a Neurospora extract. We propose that de novo DNA methylation in Neurospora cells is triggered by cooperative recognition of the minor groove of multiple short A:T tracts. Similarities between sequences subjected to repeat-induced point mutation in Neurospora crassa and A:T-rich repeated sequences in heterochromatin in other organisms suggest that related mechanisms control silent chromatin in fungi, plants, and animals.

scholarly journals Estimation of Similarity between DNA Sequences and Its Graphical Representation

2020 ◽  
Vol 9 (1) ◽  
pp. 43-51
Keyword(s):  
Sequence Analysis ◽  
Molecular Biology ◽  
Dna Sequence ◽  
Dna Sequences ◽  
Graphical Representation ◽  
Similarity Analysis ◽  
Biological Sequence ◽  
Field Of Study ◽  
Biological Sequence Analysis ◽  
Wide Range

Bioinformatics, which is now a well known field of study, originated in the context of biological sequence analysis. Recently graphical representation takes place for the research on DNA sequence. Research in biological sequence is mainly based on the function and its structure. Bioinformatics finds wide range of applications specifically in the domain of molecular biology which focuses on the analysis of molecules viz. DNA, RNA, Protein etc. In this review, we mainly deal with the similarity analysis between sequences and graphical representation of DNA sequence.

scholarly journals NanoDJ: A Dockerized Jupyter Notebook for Interactive Oxford Nanopore MinION Sequence Manipulation and Genome Assembly

2019 ◽  
Author(s):  
Héctor Rodríguez-Pérez ◽  
Tamara Hernández-Beeftink ◽  
José M. Lorenzo-Salazar ◽  
José L. Roda-García ◽  
Carlos J. Pérez-González ◽  
...  
Keyword(s):  
Quality Control ◽  
Sequence Analysis ◽  
Dna Sequence ◽  
Dna Sequences ◽  
Genome Assembly ◽  
Interactive Visualization ◽  
Hybrid Assembly ◽  
Genomic Technologies ◽  
Oxford Nanopore ◽  
Oxford Nanopore Technologies

AbstractBackgroundThe Oxford Nanopore Technologies (ONT) MinION portable sequencer makes it possible to use cutting-edge genomic technologies in the field and the academic classroom.ResultsWe present NanoDJ, a Jupyter notebook integration of tools for simplified manipulation and assembly of DNA sequences produced by ONT devices. It integrates basecalling, read trimming and quality control, simulation and plotting routines with a variety of widely used aligners and assemblers, including procedures for hybrid assembly.ConclusionsWith the use of Jupyter-facilitated access to self-explanatory contents of applications and the interactive visualization of results, as well as by its distribution into a Docker software container, NanoDJ is aimed to simplify and make more reproducible ONT DNA sequence analysis. The NanoDJ package code, documentation and installation instructions are freely available at https://github.com/genomicsITER/NanoDJ.

scholarly journals Systematics of Scleranthus (Caryophyllaceae)

2021 ◽  
Author(s):  
◽  
Robin David Smissen
Keyword(s):  
Sequence Analysis ◽  
Dna Sequence ◽  
Dna Sequences ◽  
Sequence Divergence ◽  
Morphological Characters ◽  
Dna Sequence Analysis ◽  
Its Sequences ◽  
Data Sets ◽  
Nuclear Its ◽  
Floral Characters

<p>Scleranthus is a genus of about 12 species of herbaceous flowering plants or small shrubs with a disjunct Eurasian/Australasian distribution. Monophyly of the genus is supported by the close similarity of gynoecial development of all species and consistent with nuclear ITS DNA sequence analysis. Traditionally the genus had been divided into two sections, section Scleranthus and section Mniarum. Section Mniarum is exclusively Australasian while section Scleranthus has been circumscribed to contain exclusively European species or a combination of European and Australasian species. Pollen and floral characters align the species into Australasian and Eurasian groups also supported by nuclear ITS DNA sequence analysis. Section Scleranthus as more broadly defined (i.e., sensu West and Garnock-Jones, 1986) is therefore at least paraphyletic or at worst polypyhyletic. Phylogenetic reconstructions based on morphological characters differ from those based on ITS sequences in supporting different relationships within the Australasian species of Scleranthus. Hybridisation and introgression within the genus are discussed and suggested as the cause of discordance between morphology and DNA sequence based trees. Low sequence divergence among Scleranthus ITS sequences suggests that the European and Australasian clades within the genus diverged within the last l0 million years. Biogeographic implications of these dating and competing hypotheses explaining the disjunct North-South distribution of the genus are discussed. Nuclear ITS and chloroplast ndhF DNA sequences both suggest that Scleranthus belongs to a clade within the family Caryophyllaceae consisting of members of subfamilies Alsinoideae and Caryophylloideae. Phylogenetic relationships between genera belonging to the three subfamilies of Caryophyllaceae (Alsinoideae, Caryophyloideae, and Paronychioideae) are addressed in this thesis through ndhF sequence analysis, which provides no support for the monophyly of traditionally recognised groups. Morphological character data sets are likely to always encompass multiple incongruent data partitions (sensu Bull et al. 1993). It may therefore be appropriate to combine data from DNA sequence and morphology for parsimony analysis even where the two are significantly incongruent.</p>

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